Laundry treating appliances, such as clothes washing machines, that use liquids typically provide for the removal of the liquid during one or more parts of a treating cycle of operation. A pump may be used to remove the liquid. In the case of a clothes washer, a drain pump in a sump portion of a wash tub pumps the liquid from the sump to a household drain.
An operational concern with most liquid pumps is that the pump can only be operated when there is sufficient liquid to satisfy the pump, which prevents undesirable noise generated when a liquid pump is pumping substantial amounts of air and also reduces the likelihood of damaging the motor of the pump.